According to Urban Dictionary, a girl whose natural expression is unintentionally hostile and mean-looking suffers from RBF. This girl has a stern brow that makes her look angry and irritated. Below, the emotionless eyes seem bored, contemptuous, and possibly a little disgusted towards her surroundings. Her slightly down-turned or pursed mouth says a lot without opening. The strong and apparently tense jaw completes the bitter look. She has a terrible case of RBF.